compile with gcc:

gcc -o see see.c -framework ApplicationServices -lpthread -lm

run see as sudo:

sudo ./see

run in background using nohup:

nohup ./see &

this automatically saves stdout and stderr to a file nohup.out you can change the file to something else:

nohup ./see > output.log 2>&1 &

check to see if it's running:

ps -ef | grep see

kill process: kill <PID> or kill -9 <PID>

debugging with lldb

lldb ./see
run

try to modify event tap location

CFMachPortRef eventTap = CGEventTapCreate(kCGHIDEventTap,
                                          kCGHeadInsertEventTap,
                                          0,
                                          eventMask,
                                          eventCallback,
                                          NULL);

run as sudo:

sudo ./see

check for existing event taps

ioreg -l -w 0 | grep IOHIDEventSystem

remove CGEventTapIsEnabled -> fixes seg faults

events not being recorded?

check event mask

change CGEventTapCreate:

CFMachPortRef eventTap = CGEventTapCreate(kCGAnnotatedSessionEventTap, kCGHeadInsertEventTap, 0, eventMask, eventCallback, NULL);

check event tap status

if (!CGEventTapIsEnabled(eventTap)) {
    CGEventTapEnable(eventTap, true);
    printf("Re-enabled the event tap.\n");
}

test program:

#include <ApplicationServices/ApplicationServices.h>
#include <stdio.h>

CGEventRef eventCallback(CGEventTapProxy proxy, CGEventType type, CGEventRef event, void *refcon) {
    printf("Event detected! Type: %d\n", type);
    return event;
}

int main() {
    CGEventMask eventMask = (1 << kCGEventKeyDown) | (1 << kCGEventLeftMouseDown) |
                            (1 << kCGEventRightMouseDown) | (1 << kCGEventMouseMoved) |
                            (1 << kCGEventOtherMouseDown);

    CFMachPortRef eventTap = CGEventTapCreate(kCGAnnotatedSessionEventTap,
                                              kCGHeadInsertEventTap,
                                              0,
                                              eventMask,
                                              eventCallback,
                                              NULL);

    if (!eventTap) {
        fprintf(stderr, "Failed to create event tap!\n");
        return 1;
    }

    CFRunLoopSourceRef runLoopSource = CFMachPortCreateRunLoopSource(kCFAllocatorDefault, eventTap, 0);
    CFRunLoopAddSource(CFRunLoopGetCurrent(), runLoopSource, kCFRunLoopCommonModes);
    CGEventTapEnable(eventTap, true);

    printf("Event tap created and enabled.\n");

    CFRunLoopRun();  // Run the loop to keep capturing events

    CFRelease(eventTap);
    CFRelease(runLoopSource);

    return 0;
}

if test program works, it means there might be event/run loop handling issues and/or threading conflicts.

}